Fuel vapor control device

ABSTRACT

A canister containing a fuel vapor adsorbent has a fuel vapor inlet, a fresh air inlet and a purge vapor outlet. It additionally contains a baffle between the vapor inlet and purge outlet to prevent direct communication of fuel vapors to the purge outlet while forcing the flow of fuel vapors through the adsorbent.

[451 Aug. 27, 1974 FUEL VAPOR CONTROL DEVICE 8/1972' Jones, 55/387 [75]Inventor: Robert L. Toth, Allen Park, Mich.

Primary ExaminerFrank A. Spear, Jr. Assistant Examiner-Ferris H. Lander0r FirmKeith L. Zerschling; Robert m am Am m V1. Ma r mM AE FM &

[21] App]. No.: 295,047

[57] ABSTRACT A canister containing a fuel vapor adsorbent has a fuelvapor inlet, a fresh air inlet and a purge vapor outlet.

[52] US. 55/387, 55/DIG. 28, 55/DlG. 30 [51] Int. B0ld 53/00 [58] Fieldof Searchmm' 55/74 lt additionally contains a baffle between the vapor55/DlG. 30, DIG. 28

inlet and purge outlet to prevent direct communica- ,tion of fuel vaporsto the purge outlet while forcing References Cited UNITED STATES PATENTSthe flow of fuel vapors through the adsorbent.

3,464,186 Hankison et 55/387 6 Claims, 3 Drawing Figures FUEL VAPORCONTROL DEVICE This invention relates, in general, to a fuel vaporemission control device. More particularly, it relates to a fuel systemof the automotive type, and to a device to prevent the emission of fuelvapors into the atmosphere.

Systems are known today to prevent the unwanted escape of fuel vaporsinto the atmosphere from fuel tanks and carburetor float bowls of amotor vehicle, for

' example, during hot soak cycles of the engine when the vehicle may besubjected to extreme temperature gradients. These systems in the pastgenerally have consisted of fuel vapor vent lines from the fuel tank andthe carburetor float bowl that lead to a canister containing in mostinstances activated carbon so that the fuel vapors can be adsorbed.Subsequent operation of the engine purges these adsorbed fuel vaporsback into the engine.

In the past, the canister generally was constructed with air/fuel vaporchambers at opposite ends, with the adsorbent material sandwichedbetween. The end chambers constituted air distribution manifolds forbetter presentation of the fuel vapors to the surfaces of the adsorbent.However, with such a construction it may be possible at times for thefuel vapor flow to short circuit the adsorbent and flow directly fromthe fuel vapor inlet to the purge outlet and therefrom out to theatmosphere under the pressure of the hot soak cycle.

The invention relates to a canister construction containing a bafflethat prevents the direct communication of the fuel vapors in the inletto the purge outlet and forces them to pass through the vapor adsorbent;while, however, at the same time effecting a purge of fuel vapors in anydead spots behind the baffle to the adsorbent.

The invention consists of an open celled foam material that iscompressible, the open cells being of such small porosity such that ahigh restriction to flow therethrough is provided. The majority of thefuel vapors are thereby forced to flow past the baffle into theadsorbent during the hot soak cycle. However, the small amount of fuelvapor that may become trapped in dead air spaces behind the baffle canflow through the open cells of the baffle to the adsorbent during thehigh pressure differential purge cycle.

It is a primary object of the invention, therefore, to provide afuelvapor emission control device that effectively prevents the emissionof undesirable fuel vapors into the atmosphere.

It is another object of the invention to provide a fuel vapor storagecanister with a baffled construction preventing the escape of fuelvapors'into the atmosphere and forcing them through the adsorbenttherein.

It is another object of the invention toprovide a baffle as describedabove of an open cell foam construction of small porosity providing ahigh restriction to flow therethrough but pennitting a small amount offlow during the purge cycle so that purge air can remove fuel vapors indead air spaces that may be created behind the baffle member.

A still further object of the invention is to provide a Other objects,features and advantages of the invention will become more apparent uponreference to the succeeding detailed description thereof, and to thedrawings illustrating a preferred embodiment thereof; wherein,

FIG. 1 is a schematic illustration of a fuel vapor loss control systemembodying the invention;

FIG. 2 is an enlarged top plan view of the carbon canister shown in FIG.1; and,

FIG. 3 is a cross-sectional view taken on a plane indicated by andviewed in the direction of the arrows 33 of FIG. 2.

FIG. 1 illustrates schematically a typical fuel vapor loss controlsystem for use with a motor vehicle power plant. It shows a conventionalengine 10 having mounted thereon a carburetor 12 with a fuel or floatbowl 14. The air taken into the carburetor and engine is filtered by aconventional air cleaner 16 having a suitable dry filter element suchas, for example, of the pleated paper type.

The fuel loss control system includes a vent line 18 connected at oneend to the vehicle fuel tank 20 and to a vapor storage canister 22 atthe other end. As will be explained more fully later, the canistercontains a quantity of activated charcoal that will adsorb and storeexcess fuel vapors. The vapors enter therein under slight pressure fromthe fuel tank when hot soak conditions occur. The canister has a freshair inlet 24 and a purge outlet tube or line 26 to the air cleaner.

In general operation, when the vehicle is stationary with the engineoff, and is subjected to a heat buildup such as on a warm day, theconversion of liquid fuel into vapor creates a pressure in line 18driving the fuel vapors into the canister where they are adsorbed by thecharcoal elements. Upon start of the engine, the suction in the enginecylinders creates a purge flow of vapors from the canister by the flowof fresh air through inlet 24 through the carbon elements to desorb themof vapors and conduct them through the outlet line 26 back into theengine where they are burned.

As stated previously, the invention is concerned primarily with theconstruction of the carbon canister to prevent the escape of fuel vaporsinto the atmosphere at any time. Referring to FIGS. 2 and 3, it will beseen that the canister has a hollow outer shell 30 closed at its upperend by a beaded cover member 32. The cover has an opening 34 in whichtube 26 is fixed, a fresh air inlet tube 36 connected to inlet 24, and afuel vapor opening 38 connected to line 18.

The interior of the shell 30 is partitioned into two end chambers 40 and42 by a pair of annular steel perforated screen plates 44 and 46, thespace between the screens being filled with activated charcoal or someother suitable vapor adsorbent 47. The two end chambers 40 and 42constitute fluid distribution manifolds so that the fuel vapors and airwill be evenly distributed over the entire end surfaces of the activatedcharcoal. If chambers 40 and 42 were not provided, then any flow of airdown the fresh air tube 36 would tend to return along its outer diameterto soon saturate the adsorbent to a point where further flow of fuelvapors would cause a breakthrough without adsorption. That is,

rather than spread laterally to pass through unsaturated adsorbent, thefuel vapors would pass in a shorter, easier path over the saturatedelements and, therefore, fuel vapor would pass out into the atmospherethrough the purge tube prior to the capacity of the adsorbent beingutilized.

The fresh air tube 36 extends through cover 32, manifold 40, and bothscreens 44 and 46 into the opposite end chamber 42, with a suitablespacer element 48 on the end of the tube. A dust cap 49 covers the freshair inlet end 24 of the tube, and a spring 50 located between screen 44and the cover 32 biases the upper screen against the activated adsorbentto maintain it in place.

The canister is constructed as described above so that the fuel vaporsforced into manifold 40 will pass through the activated charcoal and beadsorbed thereon. The connection of the fresh air to the end chamber 42through tube 36, with the purge outlet 34 being at the opposite endchamber 40, forces a flow of air through the charcoal from one end tothe other during the purge operation when the engine is running, therebydesorbing the fuel vapors.

The above construction is known and further details of construction andoperation are not given since they are believed to be unnecessary for anunderstanding of the invention.

With the above construction, it will be seen that it is possible attimes for the fuel vapors under pressure entering manifold 40 to bypassthe adsorbent and pass directly out to the air cleaner through the purgeoutlet 34. This naturally is undesirable since the vapors could thenpass out into the atmosphere through the air cleaner main air inlet, inthe absence of suction from the engine. Accordingly, a baffle member 52is interposed in the upper manifold 40 between the vapor inlet 38 andthe purge outlet 34 to positively prevent the escape of fuel vapors intothe atmosphere without having first passed through and being adsorbedand stored by the activated charcoal elements.

The baffle 52 in this case consists of a compressible open cell, foammaterial of an essentially rectangular shape and has a central arcuateportion merely to avoid interference with spring 50. It will be clear ofcourse that other suitable shapes may be used as desired. The open cellfoam baffle in this case has a very small porosity, which causes a highrestriction to flow through it so that fuel vapor cannot freely flowthrough the baffle member and thereby bypass the charcoal elementsduring the purge or storage operations.

The open cell construction serves many functions. In most instances, thecanister would be filled with activated carbon by weight, in contrast tovolume. Accordingly, its depth will vary for the same size canister, andit is, therefore, desirable to have a varying thickness baffle member soas to be adaptable to positively prevent leakage of vapor into the purgeoutlet 34. The open cell compressible foam construction accomodates avarying depth manifold 40 since it is a soft spongy material.

The baffle 52 furthermore because of its open cell construction permitsa purging through it of any fuel vapor that may collect in the dead airspace between the baffle and the canister wall in manifold 40.

In operation, therefore, when the engine in FIG. 1 is shut down and thefuel tank experiences a temperature gradient large enough to cause theevaporation of considerable fuel vapor from the tank, the fuel vaporunder slight pressure will pass up into line 18 and into the canisterinlet 38. At this time, as best seen in FIG. 2, the fuel vapors willflow into the space 54 between the baffie 52 and the end of chamber 40and therefrom be forced into the activated charcoal bed 47 to beadsorbed thereon.

When the engine is again restarted, the large intake manifold depressionwill cause a flow of air through the fresh air inlet opening 49 andthrough the tube 36 to the bottom manifold 42. It will then flowupwardly towards the purge outlet 34 through the activated charcoal, andthus desorb the charcoal of fuel vapors.

It can be seen, however, that while it might be possible for fuel vaporsto be trapped in the space 54 between baffle 52 and the end of manifold40, the open cell construction of the baffle 52 permits a purging of thefuel vapor through the baffle into the charcoal and around the air tube36 and finally out through the purge outlet 34.

From the foregoing, it will be seen that the invention provides a devicefor use with a fuel vapor storage system to prevent undesirable escapeof fuel vapors to the atmosphere, and that it is accomplished in asimple and inexpensive manner.

While the invention has been described and illus- 'trated in thedrawings in its preferred embodiment, it

will be clear of those skilled in the arts to which it pertains thatmany changes and modifications may be made thereto without departingfrom the scope of the invention.

1 claim:

1. A fuel vapor loss control device for use with a motor vehicle fuelsystem to control the emission of fuel vapors, comprising, a hollowclosed canister containing vapor adsorbent material centrally located toprovide chambers at opposite ends, first tube means having an air inletat one end of the canister and projecting through the canister to theother end for connecting purge air from outside the canister to theother end chamber, second tube means at the one end of the canisterconnected to the adjacent one end chamber for the purge flow of desorbedvapors therefrom, additional inlet means to the one chamber containingfuel vapors to be adsorbed at a higher pressure than the pressure levelin the second tube means thereby effecting flow therebetween, and vaporbarrier means comprising a baffle in the one end chamber between thesecond and additional inlets preventing direct communication between thetwo and forcing flow of fuel vapors through the adsorbent.

2. A fuel vapor control device as in claim 1, the baffle comprising anopen cell material of predetermined porosity providing restricted purgeof fuel vapors through it from the opposite end chamber space on theside of the baffle adjacent the additional inlet to the opposite endchamber space on the other side of the baffle.

3. A fuel vapor control device as in claim 1, the baffle comprising acompressible material rendering it universally adaptable to variabledensity loads of adsorbent.

4. A fuel vapor control device as in claim 1, the baffle comprising asoft spongy material with small porosity providing sufficiently highrestriction to flow of air and fuel vapors therethrough to prevent thefree flow therethrough, the porosity permitting the purge of air andfuel vapors from the area in the opposite end chamber behind the baffleto the other side of the baffle.

5. A fuel vapor control device as in claim 4, the baffle comprising anopen cell foam material dividing the opposite end chamber into two partseach associated with a separate inlet.

6. A fuel vapor control device as in claim 1, the end chamberscomprising vapor manifolds for evenly distributing the flow of fuelvapors to the adsorbent.

1. A fuel vapor loss control device for use with a motor vehicle fuel system to control the emission of fuel vapors, comprising, a hollow closed canister containing vapor adsorbent material centrally located to provide chambers at opposite ends, first tube means having an air inlet at one end of the canister and projecting through the canister to the other end for connecting purge air from outside the canister to the other end chamber, second tube means at the one end of the canister connected to the adjacent one end chamber for the purge flow of desorbed vapors therefrom, additional inlet means to the one chamber containing fuel vapors to be adsorbed at a higher pressure than the pressure level in the second tube means thereby effecting flow therebetween, and vapor barrier means comprising a baffle in the one end chamber between the second and additional inlets preventing direct communication between the two and forcing flow of fuel vapors through the adsorbent.
 2. A fuel vapor control device as in claim 1, the baffle comprising an open cell material of predetermined porosity providing restricted purge of fuel vapors through it from the opposite end chamber space on the side of the baffle adjacent the additional inlet to the opposite end chamber space on the other side of the baffle.
 3. A fuel vapor control device as in claim 1, the baffle comprising a compressible material rendering it universally adaptable to variable density loads of adsorbent.
 4. A fuel vapor control device as in claim 1, the baffle comprising a soft spongy material with small porosity providing sufficiently high restriction to flow of air and fuel vapors therethrough to prevent the free flow therethrough, the porosity permitting the purge of air and fuel vapors from the area in the opposite end chamber behind the baffle to the other side of the baffle.
 5. A fuel vapor control device as in claim 4, the baffle comprising an open cell foam material dividing the opposite end chamber into two parts each associated with a separate inlet.
 6. A fuel vapor control device as in claim 1, the end chambers comprising vapor manifolds for evenly distributing the flow of fuel vapors to the adsorbent. 